1) Field of the Invention
The present invention relates to a medical stent, and more particularly, to a stent that can minimize the medical side effect by preventing regurgitation of food or fluid after the stent is disposed on an internal wall of a human body.
2) Description of the Related Art
Generally, a stent is introduced into a stricture portion of an internal wall such as a blood vessel, a bilious track, and an esophagus to enlarge the stricture portion of the internal wall and maintain the enlarged stricture portion.
Such stents are generally cylindrical-shaped and classified into an elastic type and a plastic type.
The elastic type stent is self-expandable. That is, the elastic type stent is designed to be contracted by outer force and restored to its initial shape by being self-expanded when the outer force is released. The plastic type stent is not self-expandable. That is, when outer force is applied to the plastic type, it maintains its contracted or expanded states even when the outer force is released.
Such stents are variously designed according to a portion of the internal wall where they are to be disposed. For example, when the stent is for the esophagus or the stomach, regurgitation preventing means has been provided to the stent so as to prevent food or fluid from flowing upstream, thereby preventing a serious medical side effect.
Such a stent having the regurgitation preventing means is disclosed in Korean Patent No. 170220.
The regurgitation preventing means of the Korean Patent comprises first, second and third valves mounted on an inner wall of the stent and disposed at an identical circumferential length.
However, in the stent, since each of the valves is designed to be concaved in the upper stream direction and an outer edge of each valve is integrally formed with the inner wall of the stent, the valves are easily opened when the stent is contracted and expanded by outer force. Therefore, when the stent is disposed on the internal wall of the human body in a state where it is contracted, the food or fluid may flow upstream, resulting in the serious medical side effect.
Therefore, the present invention has been made in an effort, to solve the above-described problems.
It is an objective of the present invention to provide a medical stent that can reliably prevent the regurgitation of food or fluid after the stent is disposed on an internal wall of a human body, thereby minimizing the medical side effect.
To achieve the above objective, the present invention provides a medical stent comprising:
a first cylindrical body having a first inner diameter and a central axis;
a second cylindrical body connected to one end of the first cylindrical body and having a second inner diameter; and
a valve assembly for preventing food or fluid from flowing upstream, the valve assembly comprising:
first, second and third valve members that are extended from the central axis C to an inner circumference wall of the first cylindrical body and spaced away from each other at an angle of 120xc2x0 in a circumference direction of the first cylindrical body, the first, second and third valve members being provided with first, second and third passages, respectively; and
a supporting valve member for connecting lower ends of the first, second and third valve members to an inner circumference wall of the first cylindrical body.
Preferably, the supporting valve member is hemispherical, which is concaved toward a lower streamside.
Preferably, each of the first, second and third valve members comprises two overlapped layers between which the corresponding passage is defined when the food or fluid flows downstream, outer ends of the overlapped layers, which are proximal to the inner circumference wall of the first cylindrical body, being integrally formed with each other and inner ends of the overlapped layers, which are proximal to the central axis, being separated from each other.
Further preferably, the supporting valve member comprises first, second and third wings that are identically divided in the circumference direction on the basis of the central axis, and a circumference flange interconnecting outer edges of the first, second and third wings and attached on the inner circumference wall of the first cylindrical body. Each of the first, second and third wings connects a lower end of the adjacent overlapped layers of the adjacent valve members.
Further preferably, the first and second cylindrical bodies are covered with a cover member. The cover member is made of a material selected from the group consisting of silicon-based resin, a polyurethane-base resin, and polyethylene-based resin.
A gas exhaust passage is defined between the inner ends of the overlapped layers.
Preferably, the first inner diameter is greater than the second inner diameter, and a length of the valve assembly is identical to or greater than that of the first cylindrical body.
The medical stent may further comprise an intermediate cylindrical body between the first and second cylindrical body, the intermediate cylindrical body is formed of a material selected from the group consisting of silicon-based resin, a polyurethane-base resin, and based-based resin